Abstract
In this paper, the runoff system composed of hillslope runoff generation model and channel network is used, and theoretical differential equations to calculate the first- and second-order moments of discharge are derived on the assumption that the deviation from average rainfall is described by AR(1) process. The following results are obtained. The variance of discharge in a steady state is regarded as constant when the catchment area is smaller than one hundred and several tens to several hundred kilometers square. The results of this study can be applicable to the evaluation method of lumping process of models based on their stochastic response characteristics under the impact of mutually dependent rainfall inputs.
